Small radar units are almost universally employed in the United States and elsewhere by traffic authorities to monitor the speed of wheeled vehicles. In the last several years, these devices have almost always been of a small size so as to be readily hand-held. Traffic authorities have typically mounted the radar units within a vehicle as on the dash thereof so that the occupant of the vehicle may hand-hold the unit to point it in whichever direction he likes or, in the alternative, have his hands free by using whatever mount is provided within the vehicle.
Recent months have seen a considerable increase in concern for the effects of the microwaves generated by these units on the user of the device, particularly when the user is hand-holding the same. There are some indications, not yet proven, that certain cancers may be brought about by prolonged exposure to the microwaves generated by the radar unit over a substantial period of time. As a consequence, a number of users of the radar unit do not want to occupy a vehicle having such a unit on the interior thereof. In addition, because the units are typically mounted within the vehicle for ready movement between hand-held and dash-mounted positions of use, they may not always be firmly affixed within the vehicle. Should a crash occur, the unit may become loose and move at a high velocity relative to the vehicle interior. When this occurs, an occupant of the vehicle can be struck by the unit and injured. This has sparked a renewed interest in mounting of the units on the exterior of the vehicle. However, one cannot simply take an existing radar unit from the interior of the vehicle and mount it on the vehicle exterior. Current units generally are not waterproof and, as a consequence, cannot be mounted on the exterior of a vehicle. Thus, there is a need for a waterproof radar antenna that may be mounted in a hostile environment.
This need cannot be simply met by encapsulating an existing unit in some sort of a waterproof housing. Those skilled in the art will readily recognize that an oscillator is mounted to the antenna unit and when the unit is in operation, the oscillator generates considerable heat. Thus, some means must be provided to dissipate the heat without providing a path for entry of water or other contaminating material.
Furthermore, prior art construction typically include separate horn and turnstile cavity subassemblies which must be fitted together. The joint will impede heat transfer from the turnstile cavity subassembly to the horn, an obviously undesirable occurance, and can result in excessive signal noise levels.
The present invention is directed to overcoming one or more of the above problems.